It could be a few things - sometimes a device's internal firewall don't trust network traffic from a different subnet, sometimes things like file servers use broadcast traffic that is not broadcast between different subnets (so discovery wouldn't work).
There are ways around each, but the easiest solution would be to keep your wireless and your wired stuff on the same subnet. Plug your access point into the switch with everythign else and it should work without any other tweaks.
If you really want to keep things set up the way you have them: you can address the first issue by checking firewalls on all of your client devices, you can fix the second issue by setting up an mDNS repeater.